<div id="panel" class="formio-component formio-component-panel formio-component-panel " ref="component">
  <div class="panel panel-default">
    <div class="panel-heading" role="button" aria-expanded="true" aria-controls="panel-panel" ref="header">
      <h4 class="mb-0 panel-title">
        Panel
      </h4>
    </div>
    <div class="panel-body" ref="nested-panel" id="panel-panel">
    </div>
  </div>
  <div ref="messageContainer" class="formio-errors invalid-feedback"></div>
</div>